Papua New Guinea police say they have discouraged people in Port Moresby from retaliating for the killing of one of the country's most prominent business people, Sir George Constantinou.

The 75 year old was killed yesterday at a timber yard owned by one of his companies, in Gerehu, near the Tete squatter settlement.

He was set on by up to 30 youths, believed to be from the settlement.

A police spokesman Superintendent Dominic Kakas, could not say what prompted the attack, but the Post Courier newspaper reports that they had demanded Sir George's valuables.

He says there is a lot of anger over the murder and people had gathered with the aim of attacking the Tete settlement, but the Metropolitan Superintendent, Fred Yakasa, talked them out of it.

"He told the people there that this matter is now with the police and they are not to take the law into their own hands. He warned them and he actually prevented them from going. He told them four suspects have been arrested in relation to the killing, and a couple more arrests will be made soon."